Graphene material has been shown to have a mobility of more than 20,000 cm2/vs. Both microwave transistors and logic circuits have been implemented using graphene material layers. For most microwave transistor and logic circuits, it is preferred that the graphene material be deposited on a dielectric surface or a semi-insulating or insulating substrate.
To date, the primary approaches to form a graphene material layer on a material surface have involved one of three methods.
The first method that has been used to form a graphene material layer on a surface is a peel-off/transfer method in which a single layer is peeled off from a graphite crystal using tape and transferred to the substrate. See A. K. Geim and A. H. MacDonald, “Graphene: Exploring Carbon Flatland,” Phys. Today 60, 35 (2007).
CVD growth/transfer method in which graphene is formed on a film of metallic catalyst at temperatures of approximately 450-1000° C., and then transferred to a different substrate. See S. Bae, H. Kim, Y. Lee, X. Xu, J. S. Park, Y. Zheng, J. Balakrishnan, T. Lei, H. R. Kim, Y. I. Song, Y. J. Kim, K. S. Kim, B. Ozyilmaz, J. H. Ahn, B. H. Hong, S. Iijima, “Roll-to-roll production of 30-inch graphene films for transparent electrodes,” Nature Nanotechnology, 5, 574 (2010); Y. Lee, S. Bae, H. Jang, S. Jang, S. E. Zhu, S. H. Sim, Y. I. Song, B. H. Hong, J. H. Ahn, “Wafer-scale synthesis and transfer of graphene films,” Nano Letters, 2010, 490 (2010). Silicon-carbide (SiC) surface decomposition method in which a substrate of SiC, a semiconductor, is heat-treated at 1200-2000° C. to form graphene on the SiC surface. See J. L. Tedesco, B. L. VanMil, R. L. Myers-Ward, J. M. McCrate, S. A. Kitt, P. M. Campbell, G. G. Jernigan, J. C. Culbertson, C. R. Eddy, Jr, D. K. Gaskill, “Hall effect mobility of epitaxial graphene grown on silicon carbide,” Appl. Phys. Lett. 95, 122102 (2009); P. Sutter, “Epitaxial graphene: How silicon leaves the scene,” Nature Material 8, 171 (2009).
A major issue with the CVD growth/transfer approach is the introduction of defects in the graphene material film during the transfer process and the introduction of impurities into the graphene material layer during the transfer process. The CVD/growth/transfer approach is a more costly approach than an approach that would grow a graphene material layer directly on a material substrate or material layer. A major issue with graphene growth on SiC is that SiC substrates are currently available in diameters to 150 mm while silicon substrates are available in diameters to 300 mm. In addition, silicon substrates are much less costly than silicon carbide substrates.